Apparatus for use in hot water heating systems



P 29, 1964 H. L. MOHN ETAL 3,150,827

APPARATUS FOR USE IN HOT WATER HEATING SYSTEMS Filed Oct. 24, 1961 2 Sheets-Sheet 1 outdoor From Heating To Healing System Therm-9M! System INVENTO RS HENRY L. MOHN ELMER JEROME KERN GEORGE D. FRANK ATTORNEYS p 29, 1954 H. L. MOHN ETAL 3,150,827

I APPARATUS FOR USE IN HOT WATER HEATING SYSTEMS Filed Oct. 24, 1961 2 Sheets-Sheet 2 INVENTORS HENRY L. MOHN ELMER JEROME KERN GEORGE E. FRANK VW/ ZMW ATTORNEYS United States Patent 3,150,827 APPARATUS FGR USE 1N HOT WATER HEATING SYSTEMS Henry L. Mohn, York, Ehner lemme Kern, Dalinstown,

and George 1). Frank, York, Pa., assignors to York- Shipley, Inc, York, Pa, a corporation of Delaware Filed Oct. 24, 1961, Ser. No. 147,274 5 (Ilainis. (Cl. 237-8) This invention relates to an apparatus for use in hot water heating systems and more particularly, it concerns new and unique heating plant for hot water type space heating systems.

In recent years, plants for hot water space heating systems have been improved to make them more compact and to achieve the highest possible heat output. Also, they have been equipped with recently developed, highly refined, control systems for the achievement of maximum efficiency and resultant savings of fuel. While these developments have been generally satisfactory to provide the results intended from the standpoint of heating all types of buildings in an eficient and desirable manner, their use in many instances has placed the plant under unusual operating conditions resulting in failures or damage to the boiler thereof, which in turn gives rise to substantial expenditures of time and money for repair, thus mitigating the desirable features aforementioned.

One principal cause of boiler failures is the occurrence of thermal shock, i.e., the stressing of the boiler structure due to quick temperature changes or the existence of uneven water temperatures within the boiler. Thermal shock is particularly prevalent in heating systems of the type which include a night set-back conventionally arranged so that a substantial amount of the Water in the space heating system is permitted to recirculate without passing through the boiler, thus dropping the temperature of the heated space at night or during periods of non-use to the extent that in many instances the temperature of the water in the heating system approaches room temperature. In the morning, however, when there is a demand for heat, the cold system water is suddenly directed through the boiler causing a rapid temperature drop within the boiler. For example, observations have shown that the temperature of boiler water in this situation can be lowered approximately 100 F. in one minute. The stresses imposed on the boiler as a result of this rapid temperature change or thermal shock causes loose and leaky tubes, cracked ligaments between tube holes and other structural failures. Also, in conventional systems the cold return water is introduced into the bottom portion of the boiler while the hot and thus lighter water remains thereover to effect uneven temperatures between the bottom and top portions of the boiler. Such uneven temperatures also result in thermal shock by which damage may be inflicted to various parts of the boiler.

Another failure common to hot water plant boilers is the deterioration of metal surfaces and tube ends due to condensation of combustion products. The introduction of indoor-outdoor temperature control systems for hot water plants has made this problem more prevalent for the reason that in such control systems, boiler water temperature is maintained in accordance with outdoor temperatures to anticipate the need for hot water by the space heating system, and in mild weather, the water temperature in the boiler is often permitted to drop sufficiently to cool the tubes and other parts which come in contact with combustion products of a hydrocarbon fuel burner. Then, should the space heating system call for heat, the burner is ignited, the combustion products contact the cooled surfaces and water vapor, which is necessarily produced by the burning hydrocarbons, condenses on the ice boiler tubes and the like. The presence of such moisture on the metal surfaces of the boiler, particularly when accompanied by the extreme heat of combustion, presents severe problems of corrosion as mentioned above.

In addition to the deterioration and corrosion of metal surfaces due to condensation of combustion products, the corrosion of heating surfaces due to entrainment of oxygen in the system Water is a common cause of boiler failure. More specifically, in a conventional hot water plant, the passage of cold, return Water from the bottom of the boiler upwardly over the heating surfaces to an outlet located at the top of the boiler operates to liberate bubbles of air or oxygen which must move up past the heating surfaces in order to escape through a vent necessarily connected at the top of the boiler. As a result, some of the oxygen bubbles become attached to the heating surfaces and start corrosion.

Although various attempts have been made, and some successfully, to overcome certain ones of these causes of boiler failure, there has been no fully successful solution heretofore by which all of them have been circumvented while at the same time retaining the efiiciency of the plant and the system in which it is used.

A principal object of this invention, therefore, is to provide a unique method of heating water for space heating systems as well as a novel and highly effective water heating plant by which the aforementioned problems are effectively and substantially overcome.

Another object of this invention is the provision of an improved heating plant incorporating a water circulating system for the boiler thereof by which cold, return water is bypassed around the boiler so long as the temperature of the boiler water is reduced to a level at which thermal shock and condensation of combustion products might occur.

A further object of this invention is to provide a water circulation system for heating plants of the type aforementioned whereby the temperature of the water within the plant boiler is maintained evenly over all portions of the boiler so that thermal stresses as a result of such uneven temperatures are kept at a minimum.

Another object of this invention is the provision of a heating plant of the type referred to by which oxygen entrained in cold, return water may be removed immediately upon entry into the boiler before contacting the metallic heating surfaces thereof and thus reducing the corroding effect of the oxygen on these metal surfaces.

Still another object of this invention is the provision of a new and unique method for supplying heated water from a hot water boiler to a space heating system in a manner such that the boiler is safeguarded against the effects of thermal shock, condensation of combustion products and corrosion due to entrained oxygen without detracting from the over-all operating efficiency of the hot Water space heating system.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description, while indicating preferred embodiments of the invention, is given by way of illustration only, since it will become apparent to those skilled in the art from this description, that various changes and modifications can be made without departing from the true spirit and scope of this invention.

In general, the aforementioned objects are accomplished by a hot water plant having a fuel burner operable under the control of a temperature responsive device or Aquastat positioned in the boiler thereof to maintain boiler water temperature within a predetermined range, the lower limit of which is sufficiently high to prevent condensation of combustion products from the burner. Water thus heated within the boiler is fed to the space heatamass? ing system as needed through a supply conduit extending from an outlet at the underside of the boiler. The temperature of water fed to the space heating system is controlled by an outdoor thermostat operatively associated with a blendingor modulating valve arrangement interconnecting a boiler inlet conduit in the upper side of the boiler, a cold water return conduit and one end of a bypass conduit, the latter having its other end connected with the supply conduit so that proper amounts of cold, return water may be blended with the hot water in the supply conduit to attain the desired temperature of water supplied to the space heating system. The blending valve is also associated with a second temperature responsive device positioned within the boiler and arranged in such a manner that blending valve control effected by the outdoor thermostat is overridden by the element within the boiler in the event the temperature of boiler water approaches the lower limit of the range aforementioned. In this manner, boiler water temperature is always maintained within the predetermined safe temperature range and the danger of thermal shock due to the introduction of a large amount of cold return water is eliminated. Also, because the cold return water is fed through the boiler inlet positioned at the top of the boiler while hot water is fed from the bottom thereof, the boiler water is continuously stirred and the temperature thereof remains even throughout all portions of the boiler. A further feature of the present invention resides in the provision of an air vent in the top of the boiler and the position of the air vent relative to the boiler inlet assures that any oxygen bubbles entrained in the return water are removed from the boiler prior to contact with the heating surfaces thereof.

A more complete understanding of the heating plant of this invention and its method of use will be had by reference to the accompanying drawings in which:

FIGURE 1 is a cutaway view in side elevation of a preferred form of the heating plant of this invention; and

FIGURE 2 is a cross-sectional view of the blending valve adapted for use with the present invention.

Referring now to FIGURE 1 of the drawings, the heating plant of this invention is shown including a boiler generally designated by the numeral 19 conventionally provided with a fuel burner 12, a combustion chamber 14, tubes 16 supported between tube sheets 18 which establish with the ends of the boiler the usual headers 20 through which the combustion products pass to a stack 22. As will be understood by those skilled in this art, in practice, a heating plant of this type will be equipped with many components in addition to those illustrated in the drawing; such as, for example, pressure relief devices, low water cut-offs, burner igniting and control devices, among others. These components, together with various components of the space heating system with which the heating plant of this invention is intended to be used are conventional and therefore omitted to avoid confusion and unnecessary cluttering of the drawing and description.

The heating plant of this invention includes further a hot water supply conduit 24 connected at one end to an outlet pipe 25 in the underside of the boiler 10 and connected at its other end by Way of a T-coupling 26 to the inlet 28 of a circulating pump 3% having an outlet 32 for directing hot water to a conventional space heating system (not shown). Preferably, though not necessarily, a baflie plate 34 is positioned in the lower portion of the boiler 10 above the outlet 25 to assist in maintaining even temperatures throughout the boiler as will be understood from the description which follows below.

Positioned in the upper side or top of the boiler is a boiler inlet conduit 36 preferably in the form of a diffuser tube having laterally disposed openings 38 to assure even distribution and diifusion of water entering the boiler along the length thereof. Thus, it will be seen that since the upper and lower positioning of the inlet 36 and outlet 25 respectively opposes the natural tendency for hot water to rise and cold water to fall, even temperatures of water within the boiler are maintained. The eifect of the positioning of inlet and outlet conduits is assisted both by the diifusing action of the inlet conduit 36 and the baffle 34 on the basis that water cannot pass directly across the heating surfaces of the boiler from the inlet 36 to the outlet 25. Instead, the circulation of Water within the boiler will be generally throughout the entire boiler as indicated by the arrows. The entry of return water through the inlet 36 of the upper side of the boiler is advantageously employed further by the provision of a vent tube id also opening to the boiler at the top there of and connected with an expansion tank 42. In this manner, any air or oxygen bubbles which may be entrained in the return water are passed directly to the vent tube dti prior to their having come in contact with'the tubes 16, combustion chamber 14 or other heating surfaces within the boiler.

The inlet conduit 36 is interconnected with a return conduit 44 and one end of a bypass conduit 46 by a generally T-shaped modulating or blending valve 43, the other end of the bypass conduit 46 being connected to the T-coupling 26 and thus with the hot water supply conduit 24.

The details of the blending valve 4-8 are illustrated in FIGURE 2 of the drawings and as shown, the valve is provided with a housing 56 defining an inlet 52 to which the return conduit 44 is connected, an outlet 54 to which the boiler inlet conduit 36 is connected and an outlet 56 to which the bypass conduit 46 is connected. In each of the outlets 54 and 56 is a butterfly valve 58 and 60 respectively arranged to be operated by a reversible motor 62 through suitable linkage. The linkage includes an arm 64 rotatable with the drive shaft 66 of the motor, the arm 64 being connected by a rod 67 to the central arm 68 of a three arm assembly 70 pivotally mounted on the housing 50 by way of a pin 72 and a bracket 74. A lower arm 76 of the assembly 70 is connected by a rod 78 to an arm 8i fixedly mounted on the shaft 81 of the butterfly valve 66. In like fashion, the upper arm 82 of the assembly 70 is connected by a rod 84 to an arm 36 fixedly connected to the shaft 88 of the valve 58. As illustrated by the alternative extreme positions of the linkage and valve members shown in solid and phantom lines in FIGURE 2, the linkage is adjusted so that the valve 6% is in a completely open position while the valve 5% is in a completely closed position and vice versa. Also, this complementary positioning of the valves 58 and 69 will occur for all intermediate positions thereof.

Referring again to FIGURE 1 of the drawings, the burner 12 is operatively associated with a first temperature responsive device or Aquastat 9i) situated in the boiler water so that the burner operates to maintain the temperature of the boiler Water within a predetermined range. The specific range chosen may vary under different operating conditions, but in accordance with the present invention, it is essential that the lower limit of this range be sufficiently high so that the surfaces of the tubes and combustion chamber are maintained above the temperature at which condensation of combustion products occurs.

The motor 62 by which the modulating valve 48 is actuated is controlled under ordinary conditions preferably by an outdoor thermostat illustrated schematically at 92. To prevent sudden lowering in the boiler water temperature and resulting thermal shock, however, control of the motor 62 by the thermostat 92 is arranged to be overridden by a second temperature responsive element 94 situated in the upper portion of the boiler in close proximity to the inlet or diffuser tube 36. The positioning of the element 9 with respect to the inlet 36 is important since in this manner the temperature responsive element or thermostat 94 senses the lowest water tem perature in the boiler.

In use, the heating plant of the present invention is placed in operation by a master control (not shown) which efiects operation of the burner 12 to heat water in the boiler to the desired pre-established range as established by the Aquastat 90. As the space heating system calls for heat, the circulating pump 30 is operated to circulate hot water therethrough in the usual fashion. Once the boiler water temperature comes up to the setting of the thermostat M, the modulating valve motor is controlled by the outdoor thermostat for adjusting the positions of the valves 58 and 60 to regulate the temperature of water supplied to the space heating system by blending proper amounts of relatively cold water returning from the system with hot water from the boiler 10 in the supply conduit 24. In other words, when outdoor temperature requires water at maximum temperature, the modulating valve 48 will be adjusted under the control of the outdoor thermostat so that the butterfly valve 60 is completely closed while the valve 58 is completely opened so that only hot water from the outlet 25 and supply conduit 24 is fed to the space heating system. correspondingly, all return water from the heating system is fed from the conduit 44 into the boiler through the inlet conduit 36. During this time, the burner will be operated either intermittently or modulated between high and low fire under the control of the Aquastat 90 to maintain boiler water temperatures within the predetermined range aforementioned.

In the event, however, that the boiler water temperature approaches the lower limit of the desired range, control of the modulating valve motor by the thermostat 94 overides the control thereof by the outdoor thermostat 92 to bypass cold, return water through the conduit 46 to the space heating system by way of the circulating pump 30. This condition of operation is particularly prevalent during the initial operating stage of the heating plant or typically, during the morning operation immediately following a period during which the space heating system is set back to lower temperatures such as at night or other periods when the heated space is not used. Under these conditions, the burner 12 under the control of the Aquastat 9% is attempting to raise the boiler water temperature while at the same time, the space heating system is calling for hot water. If, therefore, all the relatively cold return water was circulated through the boiler and into the supply line 24 as would be the case if the modulating valve were operating under the control of the outdoor thermostat, an extremely large amount of condensation of moisture from the combustion products of the burner would take place thereby creating a critical problem of corrosion in the boiler combustion chamber and tubes. Also, the problems of thermal shock and resultant damage to the boiler are presented under these conditions. In the present invention, however, these problems are eliminated by overriding the blending valve control under the influence of the outdoor thermostat by the thermostat 94 in the boiler water. In this manner, no cold return water can enter the boiler until the temperature of the water therein is up to the desired range.

It will be seen therefore, that the foregoing objectives are completely fulfilled by the heating plant of the present invention. Because of the provision of the override control of the modulating valve as determined by boiler water temperature, the boiler is at all times protected against thermal shock and corrosion due to condensation of moisture in the burner combustion products which might arise due to the introduction of large quantities of cold water returning from the space heating system. Yet, the efficiency of the space heating system is in no way affected since the supply of hot water thereto will occur immediately as soon as hot water is available. Also, the manner in which reverse flow of water in the boiler is eflected by the upper position of the return water inlet and the lower position of the outlet along with the mixing characteristics brought about by the diffusing of return Water with water in the boiler assure even boiler water temperatures throughout the entire boiler at all times. Further, the position of the vent tube 40 with respect to the inlet 36 assures that any oxygen entrained in the cold return water will be immediately removed from the boiler water prior to coming in contact with heating surfaces thereby protecting these surfaces from the corrosion which otherwise would take place. In this manner, the heating plant of the present invention may be operated without danger of failure due to the many problems heretofore encountered in the art.

Since many changes and modifications of the specific manner in which this invention may be practiced are possible, it is to be distinctly understood that the foregoing description is not by way of limitation but illustrative only and that the true spirit and scope of the present invention is to be determined by the appended claims.

We claim:

1. A heating plant for hot water space heating systems. said plant comprising: a boiler having a plurality of longitudinally disposed tubes therein; a fuel burner in said boiler for heating Water therein; a first temperature responsive means in said boiler for controlling operation of said burner to maintain the temperature of water in said boiler Within a predetermined range; a hot water supply conduit extending from the underside of said boiler; a cold water return conduit; a boiler inlet conduit extending through the upper side or" said boiler and terminating in a diffuser tube having laterally disposed openings for distributing cold return water along said tubes in the upper region of said boiler; a cold water bypass conduit connected to said supply conduit; modulating valve means interconnecting said return conduit, said entry conduit and said bypass conduit; and a second temperature responsive means for controlling said vale means to provide circulation of cold water from said return conduit through said bypass conduit when the water temperature in said boiler is below a level at which thermal shock and condensation of combustion products occur and to provide circulation of cold water from said return conduit through said inlet conduit when the water temperature in said boiler is above said level, said second temperature responsive means being positioned in the upper region of said boiler in close proximity to said diffuser tube and substanitally aligned with said openings therein to be in the path of cold return water distributed through said openings.

2. The heating plant defined by claim 1 including further an expansion tank and an air vent extending from the top of said boiler to said tank, said air vent being in close proximity to said inlet conduit.

3. The heating plant recited in claim 1 in which said blending valve means includes a housing having an inlet connected to said return conduit, and a pair of outlets, one of said outlets being connected to said inlet conduit and the other of said outlets being connected to said bypass conduit; a valve member in each of said outlets; a reversible motor mounted on said housing; and linkage means drivingly connecting said valve members to said motor.

4. The heating plant defined by claim 1 in which said blending valve is provided with an outdoor thermostatic control for regulating the temperature of water supplied to the space heating system, said second temperature responsive means being arranged to override said outdoor thermostatic control when the temperature of water in said boiler is below said level.

5. A hot water heating plant comprising:

a boiler;

a hot water supply conduit connected through the underside of said boiler;

a cold water return conduit;

a boiler inlet extending through the upper side of said boiler;

a cold water by-pass conduit connected to said hot water supply conduit;

modulating valve means interconnecting said supply conduit, said by-pass conduit and said return conduit, said valve simultaneously proportioning the flow of return water between said boiler and said supply "conduit;

first temperature sensitive means for controlling said valve means in accordance with outside temperature;

and second temperature sensitive means positioned within said boiler and adjacent said inlet for over riding said first temperature sensitive means whenever return Water lowers the temperature of water within said boiler below a point which would promote condensation of combustion products.

References Cited in the file of this patent UNITED STATES PATENTS Sims Apr. 15, 1930 McGrath Aug. 13, 1940 Lum' June 17, 1941 Harris Sept. 23, 1941 Newton Nov. 11, 1941 Middendorf et al Dec. 26, 1961 FOREIGN PATENTS Great Britain Oct. 15, 1925 Great Britain Aug. 31, 1960 Germany Oct. 1, 1932 

5. A HOT WATER HEATING PLANT COMPRISING: A BOILER; A HOT WATER SUPPLY CONDUIT CONNECTED THROUGH THE UNDERSIDE OF SAID BOILER; A COLD WATER RETURN CONDUIT; A BOILER INLET EXTENDING THROUGH THE UPPER SIDE OF SAID BOILER; A COLD WATER BY-PASS CONDUIT CONNECTED TO SAID HOT WATER SUPPLY CONDUIT; MODULATING VALVE MEANS INTERCONNECTING SAID SUPPLY CONDUIT, SAID BY-PASS CONDUIT AND SAID RETURN CONDUIT, SAID VALVE SIMULTANEOUSLY PROPORTIONING THE FLOW OF RETURN WATER BETWEEN SAID BOILER AND SAID SUPPLY CONDUIT; FIRST TEMPERATURE SENSITIVE MEANS FOR CONTROLLING SAID VALVE MEANS IN ACCORDANCE WITH OUTSIDE TEMPERATURE; AND SECOND TEMPERATURE SENSITIVE MEANS POSITIONED WITHIN SAID BOILER AND ADJACENT SAID INLET FOR OVER RIDING SAID FIRST TEMPERATURE SENSITIVE MEANS WHENEVER RETURN WATER LOWERS THE TEMPERATURE OF WATER WITHIN SAID BOILER BELOW A POINT WHICH WOULD PROMOTE CONDENSATION OF COMBUSTION PRODUCTS. 